#!/bin/bash 

while true
do
echo "请输入成绩:"
read grade
if  [ $grade -gt 100 ] || [ $grade -lt 0 ]
then
	echo "成绩范围 0 - 100"
	continue
else
	tmp_grade=`expr $grade / 10`
	case $tmp_grade in  #注意case这里要加符号$
		10 | 9)
			echo "A"
			;;
		8)
			echo "B"
			;;
		*)
			echo "C"
	esac
fi
done